A simple model of a nitrogen atom. Inside the silver ball in the center (nucleus), there are 7 protons and 7 neutrons. The 7 electrons orbiting the nucleus are found in two electron shells since the inside shell can hold only two electrons.

Everything, both living and non-living, is made up of matter. Matter has physical and chemical properties.

Physical Properties of Matter

All matter has mass. Mass is the amount of matter in an object.

Weight and mass are not the same thing. Weight is the effect of gravity on an object. (Example: A brick has a certain mass. That brick will have a certain weight on earth, a different weight on the moon, and a third weight in outer space. The mass is the same everywhere, but the weight changes).

All matter has volume. Volume is the amount of space an object takes up.

Two different representations of the abundance of different elements in the human body. Both are logarithmic representations since, in reality, oxygen, carbon, and hydrogen are so much more abundant than anything else.